In recent years, with the development and spreading of air conditioners, such as heaters and coolers, and the increase of accommodation spaces where air conditioning devices are used, the importance of a total heat exchanger for an air conditioner that can collect the temperature and humidity through ventilation has also become increased. A total heat exchange element is incorporated in such a total heat exchanger as an element that performs heat exchange.
As the total heat exchange element, for example, total heat exchange elements disclosed in Patent Literatures 1 and 2 have been widely employed. These total heat exchange elements include partition members having heat conductivity and moisture permeability and spacing members each of which is sandwiched between the partition members to maintain a distance between the partition members. The total heat exchange elements have a basic configuration in which the partition member and the spacing member are stacked in multiple layers.
For example, the partition member is a rectangular flat plate. The spacing member is a corrugated plate whose projection plane matches the partition member and which is shaped to have a saw-tooth, sinusoidal, or substantially triangular cross-sectional waveform. The partition member and the spacing member are stacked such that the directions of the waveforms of the spacing members between which the partition member is sandwiched are alternately changed by 90 degrees or approximately 90 degrees. With such a configuration, two fluid paths, that is, a flow path through which a primary airflow passes and a flow path through which a secondary airflow passes are alternately constituted between respective layers of the total heat exchange element. That is, the primary airflow passes along one surface side of the partition member and the secondary airflow passes along the other surface side thereof.
Characteristics required for the partition member of the total heat exchange element are low air permeability between fluid paths through which the primary airflow and the secondary airflow respectively pass, high heat conductivity, and high moisture permeability. These characteristics are required to prevent fresh outdoor air taken from the outdoors into the indoors from being mixed with dirty air to be discharged to the outdoors from the indoors and to allow not only sensible heat but also latent heat to be exchanged between the primary airflow and the secondary airflow when a total heat exchanger is used. Furthermore, it is desirable that the ventilation resistance (also referred to as “pressure loss” or “static pressure loss”) when the respective airflows pass the flow paths is as low as possible. This is required to reduce power consumption of a blowing device (such as a fan and a blower) that causes an airflow to flow for ventilation and to reduce operating noise of the total heat exchanger.
As one of attempts to satisfy these required characteristics, for example, Patent Literature 3 discloses a configuration in which injection molding is applied to insert mold the partition member with a resin. With such a configuration, the area ratio of the spacing member (a resin part) to the partition member is reduced to secure heat exchange efficiency, and simultaneously the cross section of a flow path is formed in a rectangular shape to reduce the ventilation resistance.
According to such a method of using injection molding, the partition member deflects under a high humidity condition and the height of the flow path becomes uneven in the side of the primary airflow and the side of the secondary airflow, so that the ventilation resistance may be increased. Because the ventilation resistance is easily increased particularly when the height of a flow path is low, this may become an obstacle when reducing the height of a flow path and increasing the heat transfer area of a heat exchange element as a way of improving the heat exchange efficiency.
In Patent Literature 4, to solve the problem of the resistance of a flow path being increased under a high humidity condition, a moisture-permeable polyethylene-based film that is highly crystalline and has a good dimensional stability even in a high humidity condition and a paper having the resin mixed therewith are used as the partition member. However, when the moisture-permeable polyethylene-based film is used, there is a problem that, after a molded product has been removed, the film is warped or shrinks easily, and therefore the resin of the spacing member is deformed and shrinks after being demolded, so that insert-molded partition member and spacing member are deflected. As a result, the ventilation resistance may be increased.
In Patent Literature 5, it is disclosed to add an inorganic filler, such as a glass fiber and a carbon fiber, to a resin to be molded, or to use foam molding that uses a high-pressure fluid or a supercritical fluid for a physical blowing agent and causes the blowing agent to foam finely in the resin. Patent Literature 6 proposes a method of injection-molding the spacing member first and causing the spacing member to sufficiently shrink and then bonding the partition member thereto.